Polishing apparatus and method for detecting foreign matter on polishing surface

Abstract

A polishing apparatus comprises a polishing tool having a polishing surface, and a holder device (top ring) for holding a semiconductor wafer (a substrate). The polishing apparatus further comprises a color CCD camera for taking a color image of a region on the polishing surface; an image processor for determining whether or not any foreign matter exists on the polishing surface based on a condition of a color in color image data acquired by the color CCD camera; and an apparatus operation control section which in response to determination of the image processing section, stops relative movement between the semiconductor wafer and the polishing surface and separates the top ring and the polishing surface from each other.

1. A polishing apparatus comprising:
 a polishing surface; 
 a substrate holder for holding a substrate and pressing a surface of the substrate against said polishing surface while said substrate holder and said polishing surface move relative to one another so as to polish the surface of the substrate; 
 a camera for acquiring color image data of a region of said polishing surface; 
 an image processor for determining whether or not foreign matter exists on said polishing surface based on a color condition of the color image data as acquired by said camera, said image processor including
 (i) identifying means for identifying whether or not a color of each point in the color image data as acquired by said camera is identical with a color of foreign matter, which color of foreign matter has been previously stored as a reference color, and 
 (ii) determination means for determining existence of foreign matter when a total area of points, each of which corresponds to the reference color, exceeds a predetermined threshold value. 
 
 
   
   
     2. The polishing apparatus according to  claim 1 , further comprising:
 a control unit for outputting a signal to switch the reference color to another color. 
 
   
   
     3. The polishing apparatus according to  claim 2 , further comprising:
 plural types of polishing liquids to be supplied to said polishing surface, 
 wherein said control unit is also for controlling which of the plural types of polishing liquids is to be supplied to said polishing surface, with said control unit being for outputting the signal to switch the reference color to another color based which of the plural types of polishing liquid is to be supplied to said polishing surface. 
 
   
   
     4. The polishing apparatus according to  claim 1 , wherein
 the predetermined threshold values depends on a range of the color image data as acquired by said camera, a size of the substrate, or a relationship between frequency of processing the color image data and a number of revolutions of said polishing surface, and 
 said reference color has a width of color. 
 
   
   
     5. A method for detecting foreign matter on a polishing surface, while polishing a substrate by pressing the substrate against the polishing surface and moving the substrate and the polishing surface relative to one another, said method comprising:
 acquiring color image data of a predetermined region on said polishing surface by using a camera; 
 identifying whether or not a color of each point in said color image data acquired by said camera is identical to a color of foreign matter, which color of foreign matter has been previously stored as a reference color; and 
 determining that foreign matter exists
 (i) when a total area of points, each of which corresponds to said reference color, exceeds a first predetermined threshold value, or 
 (ii) when a total area of points, each of which does not correspond to said reference color, decreases to less than a second predetermined threshold value. 
 
 
   
   
     6. The method according to  claim 5 , wherein
 either of the first or second predetermined threshold values depends on a range of said color image data acquired by said camera, a size of said substrate, or a relationship between frequency of processing said color image data and a number of revolutions of said polishing surface, and 
 said reference color has a width of color. 
 
   
   
     7. A polishing apparatus comprising:
 a polishing surface; 
 a substrate holder for holding a substrate and pressing a surface of the substrate against said polishing surface while said substrate holder and said polishing surface move relative to one another so as to polish the surface of the substrate; 
 a camera for acquiring color image data of a region of said polishing surface; and 
 an image processor for determining whether or not foreign matter exists on said polishing surface based on a color condition of the color image data as acquired by said camera, said image processor including
 (i) identifying means for identifying whether or not a color of each point in the color image data as acquired by said image processor is a color of foreign matter, and 
 (ii) determination means for determining existence of foreign matter when a predetermined threshold value is exceeded by a total area of points, each of which is the color of foreign matter. 
 
 
   
   
     8. A polishing apparatus comprising:
 a polishing surface; 
 a substrate holder for holding a substrate and pressing a surface of the substrate against said polishing surface while said substrate holder and said polishing surface move relative to one another so as to polish the surface of the substrate; 
 a camera for acquiring color image data of a region of said polishing surface; 
 an image processor for determining whether or not foreign matter exists on said polishing surface based on a color condition of the color image data as acquired by said camera, said image processor including
 (i) identifying means for identifying whether or not a color of each point in the color image data as acquired by said camera is identical with a color of foreign matter, which color of foreign matter has been previously stored as a reference color, and 
 (ii) determination means for determining existence of foreign matter when a total area of points, each of which does not correspond to the reference color, decreases to less than a predetermined threshold value.